The invention relates to a process for the production of an injection nozzle for use in a device for molding an object of a thermoplastic material in an injection mold, which nozzle comprises an essentially tubular inner part forming a feed channel for the thermoplastic material, and at least one essentially wire-type heating element which is situated at a distance from the inner part and which is fitted extending over a certain length of the inner part and running several times essentially round the inner part, and which is embedded entirely inside a solid metal body lying in a close-fitting manner around the inner part, which body is obtained by placing the heating element and said metal in a molten state in a mold, so that the heating element is completely enclosed by the molten metal, and subsequently allowing the metal to set, following which, the body thus formed is removed from the mold. Such a process is known from European Patent Application 0093231.
In the known process the injection nozzle is made in one piece, by placing a helically wound heating element in a mold, then fitting a solid metal bar in this heating element, and then pouring molten metal into the annular space around the bar inside the mold and allowing it to set, following which, the nozzle thus formed is removed from the mold and a passage is finally drilled through the bar in order to form the feed channel.
A nozzle obtained in this known manner has the disadvantage that the temperature distribution over the nozzle obtained by means of the single heating element cannot be set in the optimum manner for certain thermoplastic materials with a critical temperature range.